\(\bullet \)
\(\overline{\partial ^*E} =\partial E^{(1)}\)  (see e.g., [1]});
\(\bullet \)
\(\partial ^*E \subseteq E^{(1/2)}\)  and \(\mathcal {H}^{1}(E^{(1/2)}\setminus \partial ^*E) =0\)  (see e.g., [1]});
\(\bullet \)
\(P(E,B) = \mathcal {H}^{1}(B\cap \partial ^*E)= \mathcal {H}^{1}(B\cap E^{(1/2)})\)  for any Borel set \(E;\)

